1. Field of the Invention
This invention relates to a facsimile apparatus and, more particularly, to a facsimile apparatus in which an image signal can be transmitted upon being coded by different coding methods, and in which the image signal thus coded and transmitted can be decoded and then recorded.
2. Description of the Prior Art
Conventionally, the sending and receiving of image data in a facsimile apparatus is carried out following coding by an MH (modified Huffman) coding method of one dimensional coding, MR (modified READ) coding method of partial two dimensional coding, or MMR (modified MR) coding method which two-dimensionally codes all lines of the image data. Among these, the MH coding method and MR coding method are standardized as coding methods in the G3 group, and the MMR coding method is standardized as a coding method in the G4 group.
However, since the MMR and MR coding methods basically encode correlation between line image data, there is almost no compression effect with regard to image data in which monochrome change points frequently occurs or line image data have little correlation, as in a pseudo half-tone image which relies upon the dither method. Rather, there is an increase in data up to an amount which is a maximum of six times that of the original image data. This is a significant problem in the prior art.
Accordingly, when such image data are transmitted upon being coded by the MMR or MR coding method, there is a large increase in the amount of coded data. As a result, a much longer period of time is required for sending and receiving. Another problem is that an image memory having a large storage capacity is required in order to store the coded image data or the received image data.